Cant change an items category

I am trying to change an item to accessory to use with the big butt mod that is a clothing item. This is my first time using this program. The tutorial link seems to be outdated and the sims 4 studio I downloaded must be a newer version. I clicked create a new mesh and then the cas button. i picked a clothing item that was not cc. I saved it in my documents because it is write protected in program files. The category button in the top doesnt appear to change to accessory. I go to the bottom where it says leggings and select that. I change the outfit type at the bottom to everyday, formal, athletic, etc. I click export mesh. Is there something I need to in blender? I click import mesh and then I can finally change the outfit type at the top as an accessory.Then I click save. I put the package file in my sims 4/mod folder. When I go into the game it shows up on my list of mods but when I look at the accessory its not there. Could someone help me?